Anonymous Function Declaration

Declaring functions in Loop is easy, you just use the fn keyword accompanied by it's arguments and function body. For example:

fn(int one, int two, int three) {
  // Body

If you'd like to call a function again (which is it's primary use-case of course). Then you can assign a function to a variable, which is as easy it sounds.

// Notice the "fn :="
added := fn(int one, int two, int three) {
  return one + two + three

// Now you can call the function like this:
adder(1, 2, 3) // Returns 6

Named Functions

Named functions differ from anonymous functions in that it is possible to recursively call them. Creating a named function is easy and just requires providing a name to the fn keyword.

fn double(int x) {
  x + y


"A closure is a record storing a function together with an environment" - Wikipedia

Because functions are considered first-class in Loop it means they can also contain their own environment. Creating a function automatically creates an environment for that function. Take this as an example:

closure := fn(int x) {
  num := x
  return fun(int y) {
    return x * y

outer := closure(100) // Returns a function reference
outer(10) // Returns 1000

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